The present invention relates to a method of and an arrangement separating tubular foundation piles, under water, in accordance with which a separating tool arranged in inner space of the piles penetrates through its wall.
For a long time it has been known to arrange drilling and production platforms or islands in open sea for exploiting raw materials located under the sea bottom. These islands are fixed as a rule by tubular foundation piles which are rammed into the sea bottom. Such foundation piles are driven either through the inner space of the tubular island legs or through pile holders arranged in the foot region of the drilling island legs. Then they are permanently connected to the anchoring structure by filling of the annular gap between the pile end extending beyond the sea bottom and the surrounding pile holder or island leg with concrete. When the deposits expolited this way are finally depleted, the drilling or production islands required for the exploitation become useless and form disturbing obstacles for the navigation. Several small structures standing in shallow water and anchored with only few foundation piles of small diameter and thin walls have been removed by dismounting the respective foundation piles with explosions activiated very close to the sea bottom. This method is however not applicable for structures which are anchored with many large foundation piles of great wall thickness and at great water depth. In addition, such underwater explosions which can lead to killing of living creatures in large areas are prohibited in many regions because of environmental protection measures.
In another case, after removal of the production platform a hydraulically driven separating tool is centrally placed by a crane onto the remaining structure and guided through the outwardly open drilling island leg to its foot region into the foundation pile which remains in the sea bottom. It is guided over the pile wall and produces a separation cut in the wall. This working procedure requires however the arrangement of a working frame or scaffold on each drilling island, and is generally very time consuming and expensive. It cannot be used for big drilling islands which are based in deep water, since they are anchored with a great number of foundation piles which are grouped around each drilling island leg. These foundation files are guided in pile holders arranged on the island legs, and are permanently connected with the latter after the driving by filling the annular space with concrete.